Medium Energy Physics Seminar

Conference Room R-150, Building 203, Argonne National Laboratory

Thursdays at 10:00 AM

Mohammad Hattawy

Institut de Physique Nucleaire d’Orsay, France

Deeply Virtual Compton Scattering off ⁴He

Host: Kawtar Hafidi

15 June 2015 10 am

The Generalized Parton Distributions (GPDs) open a new avenue for studying the partonic structure of target hadrons in hard exclusive reactions. The GPDs contain information on the quark/anti-quark correlations, and on the correlation between the longitudinal momentum and the transverse spatial position of partons. The Deeply Virtual Compton Scattering (DVCS), i.e., the leptoproduction of a real photon where the photon is emitted by the target hadron, has been a prime reaction for studying the GPDs. In particular, in the beam and target spin asymmetry measurements, the interference of the DVCS and Bethe- Heitler (BH) processes (where the photon is emitted from the incoming or outgoing electron) is used to access Compton form-factors that are combination of GPDs. In this talk, we present the first exclusive measurement of the DVCS process off 4He with a longitudinally polarized electron beam of 6 GeV using CLAS detector in the experimental Hall-B at Jefferson Lab. The ⁴He is of particular interest since the number of the Compton form-factors is reduced to one because of its spin zero. The aim of this study is to understand the nuclear medium modifications of parton distributions. In our experiment, the CLAS detector was upgraded with a Radial Time Projection Chamber (RTPC) to detect the low energy recoil nuclei, and an Inner Calorimeter (IC) to detect the forward going photons. The details of the data analysis and the results of the beam spin asymmetry will be discussed.

Kawtar Hafidi, MEP Seminar Chairwoman (630-252-4012, [email protected] mail)

Debbie Beres, Secretary (630-252-4100, [email protected] mail)

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Paul E. Reimer
[email protected]
26 March 2015